Electrostatic microphone



A ril 17, 1962 R. GCBRIKE 3,03 7

ELECTROSTATIC MICROPHONE Filed July 50, 1959 INVENTOR. 0204) GER/K!United States Patent 3,030,457 ELECTROSTATIC MICROPHONE Rudolf Gtirike,15 Gregor Mendelstrasse, Vienna, Austria Filed July 30, 1959, Ser. No.830,558 Claims priority, application Austria Aug. 7, 1958 Claims. (Cl.179111) This invention relates to electrostatic microphones having astressed diaphragm with multiple support. In a known construction thesupport is pointwise and the support points are formed by embossing,electrolysis, milling (in the case of metal) or by casting (in the caseof varnishes etc.) in the conducting or non-conducting material of thediaphragm or of the counterelectrode. This construction has thedisadvantage that the manufacture of the multiple-supported diaphragm orcounterelectrode with numerous support points is very complicated andexpensive.

Its also known to divide the vibrating area of the diaphragm intoseveral, separate zones and to provide a continuous support for theresulting surface portions of different configuration. Such supportswere formed, e.g., by adhesively connected thin strips of paper. Thisresulted in a substantial decrease in the sensitivity of the microphone.

In another known construction the countersurface (counterelectrode) isprovided with fine, raised, preferably linear ribs, which may consist oftextile or silk fibers.

The invention provides a solution which is simple in manufacture anddoes not adversely affect the sensitivity and is characterized in thatat least one plastic thread is wound as a support on the electrode sothat the thread forms single, preferably parallel lines of support forthe diaphragm.

According to another feature of the invention the portions of theplastic thread applied to the electrode are evenly spaced. Thecounterelectrode may be formed with evenly spaced notches at oppositeedges and a thread lying in these notches may be wound on thecounterelectrode.

Nylon or Perlon in a thickness of 20-40 microns is particularly suitableas a thread material.

By the measure adopted according to the invention the industrialmanufacture of such microphones is substantially simplified because thethread can be continuously withdrawn from a supply bobbin and it is evenpossible to perform the entire winding operation with a very simple(bobbin) winder, in which several electrodes can be gripped one besidethe other. In the case of the lastmentioned one of the knownconstructions it is either necessary to adhesively connect individuallengths of thread in a laborious operation or, where a continuous threadis used, each turn of the thread must be individually adhesivelyconnected.

Two particularly suitable embodiments of the invention will be discussedby way of example with reference to the accompanying drawing, in whichFIG. 1 is a top plan view showing a diaphragm according to the inventionand FIG. 2 is an enlarged sectional view thereof.

FIG. 3 shows another possibility of arranging the threads.

A thread 1 is wound around the counterelectrode so that the notches 2milled into the edge of the counterelectrode provide for an equalspacing of the several portions of the thread. The diaphragm, consistingof insulating material, particularly of a thermoplastic, and vaporcoatedwith conducting material on one side, is adhesively connected to thethus wound counterelectrode the necessary stress is suitably applied tothe diaphragm by giving the counterelectrode a small camber. FIG. 2 is ahighly enlarged sectional view of the microphone according to theinvention. 3 is the diaphragm, 1 the thread 20-40 microns thick, 4 thecounterelectrode and 5 are the air passages.

Using the same reference characters, FIG. 3 shows a counterelectrodewhich has notches 2 on the parallel longitudinal edges. The thread 1extends in a Winding course over the counterelectrode and through thenotches, i.e., it extends on the upper side of the electrode parallelthereto. The underside of the electrode has only short portions ofthread at the edges.

I claim:

1. In an electrostatic microphone; the combination of a stresseddiaphragm, an electrode having opposite edges formed with equally spacednotches therein, and at least one continuous plastic thread wound with aplurality of turns on said electrode and retained by said notches,sections of said turns extending across at least the surface of saidelectrode facing toward said diaphragm and forming single lines ofsupport between said electrode and said diaphragm.

2. In an electrostatic microphone; the combination of an electrodehaving opposite edges formed with equally spaced notches therein, atleast one continuous plastic thread wound with a plurality of turns onsaid electrode and passing through said notches with at least onesection of each turn of said thread extending across one surface of theelectrode between said opposite edges of the latter, and a stresseddiaphragm extending over said one surface of the electrode with saidsections of the plastic thread forming spaced lines of support betweensaid electrode and diaphragm.

3. In an electrostatic microphone; the combination as in claim 2,wherein said plastic thread wound on the electrode has sections thereofextending across the other surface of the electrode between saidopposite edges and alternating with said sections of the threadextending across said one surface.

4. In an electrostatic microphone; the combination as in claim 2,wherein said plastic thread wound on the electrode has sections thereofextending along the other surface of the electrode between successivenotches in the same edge of the electrode and alternating with saidsections of the thread extending across said one surface.

5. In an electrostatic microphone; the combination as in claim 2,wherein said sections of the thread are parallel to each other andspaced apart by equal distances.

References Cited in the file of this patent UNITED STATES PATENTS1,975,801 Rieker Oct. 9, 1934 2,824,178 Bobb Feb. 18, 1958 2,878,323Bobb Mar. 17, 1959 2,934,611 Lindenberg Apr. 26, 1960 2,935,575 Bobb May3, 1960 FOREIGN PATENTS 825,997 Germany Dec. 27, 1951

